Conventionally, a bicycle is provided with a transmission apparatus installed on the crankset and rear wheel axle to ensure efficient cycling.
FIG. 1 illustrates a conventional bicycle crank transmission apparatus.
Referring to this, the conventional bicycle crank transmission apparatus (100) includes multiple chainrings (110) of different sizes to be installed on the bottom bracket of the bicycle; a front derailleur (120) which, when coupled to the frame (F), moves the chain placed on a certain chainring (110) to another chainring (110); and a shift lever (140) which, coupled to the front derailleur (120) by wire (130) and mounted on the handlebar of the bicycle and which serves to manipulate the front derailleur (120).
However, a problem with the conventional bicycle crank transmission apparatus (100) is that it frequently falls off from the chainring (110) during a gear shift because of the shifting mechanism which forces the chain to be moved. To put the chain that fell off back on the chainring (110) is a difficult task for children a user. Furthermore, while the user is putting the chain back on, their hands or clothing can get contaminated by the lubricant applied to the chain.
Moreover, another limitation of the conventional bicycle crank transmission apparatus (100) is that it is difficult to be made smaller and lighter in weight because it has multiple chainrings (110) stacked in layers and is provided with the shift lever (140) separately as it is coupled to the front derailleur (120) by the wire (130).